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A241694
Number of Carlitz compositions of n with exactly four descents.
2
5, 22, 72, 204, 510, 1168, 2516, 5140, 10054, 18976, 34707, 61776, 107374, 182697, 304982, 500455, 808462, 1287499, 2023697, 3142604, 4825797, 7333862, 11037829, 16462497, 24345385, 35716339, 52005295, 75186849, 107973181, 154071381, 218524581, 308162131
OFFSET
12,1
COMMENTS
No two adjacent parts of a Carlitz composition are equal.
LINKS
MAPLE
b:= proc(n, i) option remember; `if`(n=0, 1,
convert(series(add(`if`(i=j, 0, b(n-j, j)*
`if`(j<i, x, 1)), j=1..n), x, 5), polynom))
end:
a:= n-> coeff(b(n, 0), x, 4):
seq(a(n), n=12..50);
CROSSREFS
Column k=4 of A241701.
Sequence in context: A246211 A000345 A011846 * A220733 A338707 A058750
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Apr 27 2014
STATUS
approved